1. Field of the Invention
The invention relates to the control of document sorting machines. It relates particularly to systems employing black band detectors of use in detecting batch separator documents, or black band documents, on which a special black band is printed. When such a document passes certain detectors, signals generated by the detectors are provided to logic processing apparatus which determines from the signals when a document is a black band document and provides signals accordingly to control equipment enabling further spearation of the batches of documents in the sorting processes.
2. Description of the Prior Art
Among the prior art devices for separating documents into batches are black band detectors employed in cooperation with reflective type sensors which operate when they detect a decrease in reflected light from the black band portion of the document. Disadvantages found with the reflective designs include a need for periodic adjustment by field engineers, or other technical personnel, to maintain reliable operation. Another disadvantage of the prior art is that the mechanical arrangement is such that it is necessary to place a deflector in the transport path to position passing documents close to a focal plane at a fixed distance from the sensor assembly.
Designs based on detecting changes in light transmitted through a document, in accordance with the present invention, overcome the above mentioned shortcomings of the prior art while providing additional features which enhance overall operation and performance.